Warhammer 40K: System Error, I Summoned the Arch-Traitor!

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"We must use a war to remind this young xenos civilization what proper respect for the strong looks like."

Horus's voice was quiet. It landed like a warhammer on an anvil.

"We will beat them to the negotiation table."

Guilliman didn't respond immediately. He stood before the holographic star chart with his arms crossed, gaze sweeping back and forth over the yellow sphere of influence spreading across the south.

He agreed with Horus's assessment. The Tau Empire needed a lesson, a clean, efficient, localized war that would crush their illusions completely. Only after that war was won would the initiative at the negotiation table truly rest in the Imperium's hands.

The question was where.

The Warmaster read the Lord of Ultramar's hesitation.

He said nothing. He simply extended one finger and traced it across the holographic star chart, gliding past system after system, through the Imperium's golden defensive lines, over the purple threat markers of the Tyranids, until his fingertip stopped on a world flagged in red.

"Agrellan Gulf."

A hunter's certainty ran through Horus's voice.

"This was once Imperium territory. Now it belongs to the Tau Empire."

Guilliman's gaze dropped to those coordinates. One eyebrow lifted.

The planet's position was too sensitive to ignore. It sat in the buffer zone between the two powers, the first hard bone the Tau Empire had gnawed off during their outward expansion. If the Imperium suddenly launched a high-intensity localized war and took back Agrellan Gulf with thunderous speed, the Tau Empire could not sit idle. They would send reinforcements. Their main force would be drawn here.

And Horus intended to turn this planet into a stage.

A stage where the Tau Empire would witness the Imperium's military might with their own eyes.

"The commanding general."

Guilliman turned, his gaze settling on Horus.

He didn't voice the second half of the question. The answer was already written in Horus's bright eyes.

The Warmaster smiled.

"I'll take that role. This war is mine to lead."

Guilliman studied his brother's smile. Two seconds of silence. Then he smiled as well, no hesitation, no worry, only the kind of trust that ten thousand years hadn't managed to wear down.

"Your ability is something I have never doubted, brother. After all, you were once the Warmaster."

The moment those words landed, the office went quiet.

"Ahem."

Horus cleared his throat. The smile on his face turned a little awkward, a little resigned.

"Let's not bring up the past."

His gaze drifted, almost casually, toward the corner where Konrad Curze was standing.

Horus threw an arm around Curze's shoulders.

"Konrad, brother — how about you come along?"

Curze raised one eyebrow.

"Help you spread terror among those xenos?"

"Fear tactics may prove especially effective against a young civilization." Horus's tone brimmed with confidence, the bone-deep mastery of a man who had made war into an art form. "And I don't plan to bring an excessive number of troops. Fewer forces, faster strikes. I want a war so swift they won't have time to react."

Curze was quiet for a moment.

Deep in those hollow eye sockets, his dark pupils shifted, like he was actually running the numbers.

Then he nodded.

"Fine. I've got nothing better to do anyway. Been holed up too long. Time to get some air."

He said this without a single glance at Sevatar standing behind him, whose expression was screaming every word of you having nothing to do clearly didn't account for me.

Guilliman watched the exchange and nodded gravely.

Two primarchs.

Horus leading the assault. Curze layering in terror.

Add veteran commanders like Loken and Sevatar, soldiers who had survived more wars than most men had years, and what awaited the Tau Empire forces in the Agrellan Gulf wasn't a war anymore.

It was annihilation.

"I'll draft a full operational plan immediately." Guilliman's voice snapped back to efficiency. "I'll also reassign three new full-strength Primaris Astartes Chapters to you. Fresh blood, all of them — elite warriors built with Primaris technology, just finished their final training on Mars. They haven't bled in their first battle yet. Let them use the Tau Empire to find their edge."

"However—"

Guilliman paused. His gaze moved past Horus to Kaelen in the gray robe standing at the back of the room.

"You'll need to second Kaelen to me."

He said it to Horus.

"I need his capabilities. His knowledge of the Plague Fleet's attack vectors. His read on Mortarion's operational patterns."

Horus didn't answer.

His fingers tapped the tabletop in a slow, steady rhythm, like he was calculating something.

Then he looked at Kaelen.

"Kaelen. Your call."

"No objections."

Kaelen shrugged.

He was a brick. You put him where the wall needed him. Horus, Guilliman, either worked. And Guilliman wasn't wrong: when it came to dealing with Mortarion's Plague Fleet, the intelligence he was carrying was worth more than an extra regiment of Astra Militarum.

"Once the war against the Tau Empire is finished..."

Guilliman looked back at Horus.

"Brother, I need you to reach me as fast as possible. Ideally hit Mortarion's fleet from the flank, or the rear. Hit them hard."

"I will end the war quickly."

Horus inclined his head, voice calm and certain. The words were for Guilliman, but also for Kaelen, a quiet promise that neither of them would be kept waiting long.

With the plan set, primarchs didn't linger.

In less than 1 Terra-standard day, Horus and Curze had boarded the expedition fleet's flagship waiting in orbit. Engine ignition tore through Macragge's night sky. The ship shrank to a point among the stars, then vanished at the far end of the southern lane.

Out of concern for his friend's safety, Horus left the old knight Kullen behind.

---

"Kaelen, I've just finished my work. Walk with me."

The next morning, after grinding through a mountain of military affairs reports, Guilliman extended the invitation to both Kaelen, sitting quietly in the corner with a book, and to Kullen, watchful as a hawk beside him.

Neither the mortal nor the old knight refused. The three of them left the office with its holographic projections and endless data reports, moved through solemn corridors, and walked out into the rear garden of the Regent's palace.

This garden was where Guilliman had come most often to clear his head, ten thousand years ago.

It still was.

Only far less frequently now. War, governance, decisions without end, they had drained nearly every drop of the Lord of Ultramar's time and energy.

Kullen kept a precisely measured distance, three meters behind, his old eyes scanning every shadow that might hide something dangerous.

The mortal and the primarch walked side by side up front, talking freely, no distance between them.

Guilliman had been frustrated lately.

Because no one talked to him.

His sons, those loyal Ultramarines, were too awed to open their mouths. Perfect warriors. Perfect executors. Terrible conversationalists. The only one with the nerve to actually approach him was Cato Sicarius, and Sicarius's emotional intelligence was something that genuinely defied description.

The pressure had nearly driven the Lord of Ultramar to madness.

He'd once taken out the skulls of sons who'd died in battle ten thousand years ago, sat alone in his office, and talked to them. As if the hollow bones still held the men who had once lived inside them. As if those long-dead sons were still listening.

Kaelen had picked up on it.

So he talked. He brought up his time in Imperium Nihilus, what he'd seen in the dark corners of the empire, what he'd heard about the Lion. He told the stories the way only he could, in that street-sharpened style of his: absurd comparisons, perfectly timed complaints, irreverent jabs woven through the whole thing. The Lord of Ultramar laughed. Actually laughed. That face, which the weight of command had nearly stripped of all expression, finally broke into something real.

Guilliman's mood lifted.

The three of them moved slowly through the garden until they came to a small pavilion.

Two statues stood inside.

Consul Konor, majestic, kind. Lady Euten, gentle, unyielding. Their stone eyes looked out across ten thousand years of time, still watching over the great man they had raised.

In fact, statues of Roboute Guilliman's adoptive parents were scattered throughout the garden. Ten of them, at least ten, placed in every corner, so the Lord of Ultramar could stop and remember whenever he needed to.

Ten thousand years hadn't dimmed that love.

If anything, it had deepened. Settled into the bone.

Guilliman stopped in front of the statues.

He looked up at their faces for a long time and said nothing.

Then he turned to Kaelen.

"Kaelen. Since you know me — I'd like to ask you something."

His voice had shed a little of its usual authority. In its place was something rarer: a trace of genuine, almost boyish curiosity, the kind he only let through in front of people he actually trusted.

"In your view, which of my adoptive parents had the greater influence on me?"

Kaelen was quiet for a moment.

His gaze moved between the statue of Consul Konor and the statue of Lady Euten, slow and deliberate, like he was weighing something carefully.

His eyes settled on Lady Euten.

That remarkable woman who had held the Lord of Ultramar's humanity together, his warmth, his emotions, his capacity to feel, through gentleness and an iron will.

Then he spoke.

"If we're talking about the fundamental force that shaped your life's work and the code you live by, it was your adoptive father. Consul Konor Guilliman of Macragge."

➤ Next: T'au: Damn, Why Is the Human Imperium So Evil?

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